Multipactor oscillator and amplifier



'Aug. 31, 1 937. P; T. FARNSWORTH IUL'I'IPAC TOR OSCILLATOR ANDAMPLIFIER Filed Feb. 24, 1936 2 Sheets-Shoat 1 I U I INVENTOR,

PHILQ 1: mmvswon TH.

- Aug.3l, 1937. P. T. FARNSWORTH 2,091,439 IUL'I'IPACTOR OSCILLATOR ANDAMPLIFIER Filed Feb; 24, 1936 f 2 Sheets-Shoot 2IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIINVEN'IOR, PHILO- 1: rAR/vswoRrM ATTORNEYS.

' Patented Aug. 31,. 1937 "2 091,439

amass m'ri'rsc'ron oscm'ron AND smu Phiio '1'. San Francisco, Calif.,as-

, I slgnor to Farnsworth'lclevision Incorporated, San Erancisco, Calif.,a corporation of California' f Application February 24,1936, Serial No.65,465 in Claims. (c1. zso- -zn My invention relates to a multipactoroscillator and amplifier, and more particularly to a means and method ofutilizing secondary emission for the production of electron multiplica-55 Figure 1 is a diagrammatic sectional view, to-

gether with a multiplier circuit, of a preferred form embodying myinvention.

Flgureii is a sectional view and circuit diagram embodying thetube'shown-inl lgure 1, connected The impressed It. I". initiates, bythe multiphtionp tobe a self-oscillator. 6

This device operates broadly on the principles Figure 3 is a" view,partly in section and partly "set forth in my prior application, SerialNo. 692,- in elevation, of a multlpactor structure utilizing 1585, filedOctober '1, 1933, for an Electron multifour electrodes dmcribing acylinder around the plying device", and my prior application, Serialcentral anode.

No. 106,965, flied January 17, 1934, for fMethods Figure 4 is asectional view taken as indicated 10 of electron multiplication". by theline 4-4 in Figure 3, together with an op- The present application dealswith a multieratingcircuit attached thereto.

pactor structure and method of operation where The operation 0! myelectron multiplier or multiplication and collection are separated. Themultipactor, as I desire to call my device, depresent device is, incommon with the previous pends upon the transference of energy betweentypes of multlpactors described by me, capable an oscillating cloud ofelectrons" and an'oscillatof producing amplification by electronmuitipli ing E. M. I"., usually established between apair cation, and byproper connection can be made of opposed cathodes, treated or otherwisecato generate self-sustaining oscillations. pabie of producing secondaryelectrons at a re.-

The primary object of this invention is to protio greater than unitywhen impacted by the oso vide an improved means and method ofabstractcillating electron cloud. If the energy transfer ing power froma multipactor. be from the oscillating E. M. 1". to the electron Otherobjects of my invention are: To procloud. the electrons strike thecathodes and give vide an oscillator which will convert direct cur-'-rise to the secondary electron multiplication pherent energy atextremely high enlciency; to pronomena. If, on the other hand, energy isabvide an oscillator or the high vacuum type which sorbedfrom theoscillating cloud of electrons, the. is not subject to the instabilityand inconsisoscillating fleldbetween the cathodesis intensitencies whichsuch phenomena inti'iz duce; to profled. and the tube may sustainoscillations in the vide an oscillator and amplifier whichhas no cathodecircuit. i heated electrode of the thermionic type, and I .Thejpresentinvention concernsa device where so 'which is correspondingly free ofthe difiiculties both of these phenomena are produced in diiIerandcomplications introduced by cathode heating but adjacent structures,electrons being ing surfaces; to provide an electron multiplier passed,preferably through a common cathode, structure which is capable ofgenerating. selffrom one tothe other. v 5 sustained oscillations andwhich may be readily Considering then, first, the condition wheremodulated; to provide a means and method of energy is transferred fromthe applied E. M2. 1'. operating a combined multipactor and output tothe electron cloud. I find that when the period structure having acommon cathode;'to provide of the oscillating cloud of electrons isclose to a ineansand'method of creating, an oscillating the resonantfrequency of a circuit connecting 4o cloud, of electrons, and a meansand method of the cathodes, that-the tubeacts as a highly efa absorbingpower from this cloud; and to provide flcient electron multiplier and.in many cases.

asimple andeflicient multipactor tube. will self-oscillate if energy iswithdrawn from. My invention possesses numerous other'objects themultipactor structure and used, at least in and features of advantage,some'of which, to-' part.'to supply the oscillating I. M. I". appliedgether. with the foregoing, will be set forth in to the cathodes, energyin this caserof course, 45 the following description of specificapparatus being supplied from a D. C. source applied to embodying andutilizing my novel method. It an anode preferabLv positioned betweenthetwo is therefore to .be understood that my method is cathodes. 1applicable-to other apparatus, and-that I do not When the period of theoscillating. cloud of to limit myself; in any way. to the apparatus ofthe electrons is close-to th res na t freq y of so present application.as I- may adopt various other the circuit connecting the cathodes, it isfound, apparatus embodiments,' utilizing the method, experimentally.that the tube generates oscilwithin the scope ofthe appended claims.lations which are largely determined by the res- Referring tothedrawings; onantfrequency of the tuned circuit.

cation process, a cloud of electrons of the proper phase to absorbenergy from the oscillations.

This cloud of electrons would oscillate by itself at approximately thesame frequency as that of 5 the circuit, except for the fact that the R.F. itself accelerates the cloud and makes the trip across the tube lessthan a half period of the tuned circuit. The mere fact that theelectrons are. speeded up insures that they strike the oathode. Thereturning group of electrons also make the trip in slightly less thanone-half cycle. The result is that the fastest electrons very rapidlyget out of phase with the potential. The electron distribution in thecloud, however, reshapes itself at each half period because the rate ofmultiplication is large compared to the 'amount of phase shift.

The process results, however, in electrons being fed from themultiplication phase into the opposite phase wherein an electron isdecelerated rather than accelerated by the R. F. Electrons in this phasedo not strike the cathodes at all, but continue to oscillate betweenthem, delivering energy to the external circuit as they are slowed downby the R. F. If the probability of an electron striking the anode issuffioiently small, equilibrium current results when the electrons arefed from the multiplying phase into the energy-giving phase at the samerate as the electrons are multiplied at the cathode, and electrons ofthe energy-giving phase never strike the cathode until they have givensubstantially all their energy to the oscillating circuit. a I maydesire, however, as in the present case, not to abstract power directlyfrom the multipactor structure, but to utilize directly a portion of theoscillating cloud of electrons in another structure closely associatedwith the first, and

very emcient secondary emissive surface, with ratios as high as oneprimary to six secondaries, when impacted at the proper velocity, but Ido not wish to be limited to such'a formed surface as even untreatednickel has been found to have an emission ratio greater than unity; andany surface, formed or unformed, having such a ratio will besatisfactory, although, of course, multiplication can be accomplishedwith alesser number of impacts with the materials having'higherCollector cathode 9 is supported on a lead II passing through a seal I 2in the end of the tube.

.collector cathode 9, however, differs from multiplier cathode 2 in thatits inner surface is preferably of a nature that it will not emitsecond- I aries, at least secondary emission will be-reduced to aminimum;- and I have found that a carbonized nickel surface in thisposition will-prevent, to a large extent, secondary emission.

After the electrodes have been assembled as described, the tube is, ofcourse, baked out. de-

withdraw the multiplied output from the second 40 structure.' Myinvention may be more fully understood by direct reference to thedrawings, which show an improved type of multiplier structure connected,

in Figure l, as a direct electron multiplier.

The tube itself comprisesa conventional type of multipactor, as hithertodescribed and claimed by me in the applications referred to above, com--structure.

The cup-shaped cathode 2- may be mounted in any convenient manner, suchas on a lead 3 passing through a reentrant stem 4 in the end of thetube.

The opposing cathode may conveniently be located at approximately themidpoint of the tube,

and comprises ascreen cathode l5 extending across 50 the tube andpreferably positioned within a cathode cylinder 6.

Between the two cathodes is positioned a multiplier anode l preferablyin the form of a cylinder whose walls are-in the same projected surfaceas determined by the. walls of the cup 2 and the cylinder 8. The,interior of the cathode cup 2 and the surface of the cathode screen- 5are preferably sensitized so that they will emit secondaries at a ratiogreater than unity, when impacted, and this sensitization, which isperformed in order that the highestpossible ratio may be obtained, maybe accomplished by forming the cathodes of silver, oxidizing the silver,and depositing caesium thereon, for example. Such a surface makes anections.

'gether through separate radio frequency chokes gassed, evacuated, andthe surfaces formed on cathodes 2 and 5.

For multiplication, the tube isconnected as shown in Figure 1. On themultiplier end radio frequency is fed into the input connection llthrough a blocking condenser II, to cathode 2 through lead 3, andcathode 2 is connected through a tunable resonant circuit II to thescreen cathode. 5 through suitable ground con- Anodes I and ID areconnected tol'l to a D. C. anode source l8, the opposite end of which isalso grounded, the positive end of this source being connected to theanodes.

The collector cathode 9 is connected through an output resonantcircuit'2ll to ground, and the output may be taken from this cathodethrough blocking condenser 2|. All that is necessary to 'set the tubeinto oscillation is to energize the anodes land ID, as there will be, inthe space between cathodes 2and 5, a suiiicient number of free electronswhich are accelerated toward one or both of the cathodes by thepotential of -the anode, to strike thereon and cause the initiation ofsecondary emission.

If, then, a radio frequency is applied between the cathodes 2 and 5 andcontrolled by means of the tuned circuit l8, and the time of flight ofthe electrons between cathodes 2 and I is adjusted by means ,of placingupon the anode I the proper potential so that the time of flightcorresponds to the period of the input, oscillations of theelectrons'between the two cathodes will occur and repeatedimpacts withthe oathodes will take place with the release of secondary electrons ateach impact.

Inasmuch as the field between the cathodes is so arranged either by theconstruction of the cathodes,.-as shown, or by an extemal' electricfield, as has been pointed out in my Prior cited applications, certaindefinite members of traversals will take place before collection byanode l from previous multipactor -1 1- ha e, and therefore are 70 mon'tune'd circuit occurs, and a d te multiplication factor will be reachedbefore equilibrium current is arrived at in the tube. Thus, there willoccur within the multiplier end of the tube, electron inuitiplica-' 5tion: and I prefer, with this type of tube, to soadiust the constants onthctwo cathodes'and the anode of the multiplier structure, that amaximum equilibrium current is reached.

The structure just described, however, diiiers structures in that thecentral cathode K is apertured. This means that at each time theelectron cloud reaches the plane of cathode I, acertain number ofelectrons impact and create secondaries which are -.used to continuethe'multiplication process, but others oi the electrons pass directlythrough-the ape'r-. ture in cathode l and enter the output structurecomprising cathode I, anode Ill and cathode I. r In this structure,however, conditions aredii- 2 1mm. The output cathode O has been treatedto prevent secondary emission, and ii cathode I is connected to cathode5 through a tuned circult 2", the electrons passing through the cen--tral cathode 5 will tween cathodes 9 and 5, and energy will be absorbedfrom them as they oscillate between cathodes O and I: in other words, inthe output structure, energy is being absorbed from the electrons. 1

The advantage gained in taking energy out of thetube in this manner isthat phase shift of the oscillating-electrons ln-the output structure isunimportant. In other words, any electrons in the output portion of thetube which get out in a positionto absorb energyirom the oscillations,strike the oathodes and are absorbed by them, and as the potentialon theanodes in each portion oi! the tube can be adjustedso that the electronoscillation frequency coincides with that of the tuned circuits andwith, the E. M. 1". to be amplified, both structures operate completelyin phase.

It will be understood, of course, that'the output structure does, in nosense, 4'5 multiplication;

' sorbs all electrons striking it, and will not release secondaries. Inother words, by using symmetri-j cal structure operating in phase, Ihave separated multiplication and output. I create the oscillation ofthe electron cloud and'supply power to it, in one structure,withmultiplication; and I absorb power from the cloud, withoutmultiplication. in the other structure. I

I'have thus eliminated thenecessity within the multiplier structure ofdeveloping a largeout-of-phase component, in order that power heabsorbed from the cloud. In other words, it is necessary, as aboveexplained, in order to create 00 an output from the ordinary multiplier,to absorb power from which is' out of phase with the multiplying cloud.In this case only enough power is absorbed to continue multiplication. 5Such an arrangement leads to a high conver- ,sion'emciency, and alsoleads to a high efliciency sell-oscillator. For example, I have shown acircult in Figure 2 where the output cathode 9 is coupled to the inputcathode 2 through a com- 22, an intermediate tap 24 bei taken from theinductance of the tuned circuit to the central. apertured cathode 5.Such a connection causes self-oscillation of the multiers'tructurecomprising cathodes 2 and t and 7 anode-I, with additional power beingabsorbed in fures 3 and ,4. In

' cathode, however,

oscillate back and term he to become a sell-oscillatory create electronit is in eflect a multiplier strue- 'ture with the exception that thecathode 9 aba component of the electron.cloudthe" I together with anodeII. This power is fed back to the input structure, and thus the E. M.Eds regeneratively amplified and an extremely ei fi cient oscillatorresults.

- 'Another structural embodiment utilizing 'my method of electroncollection is shown in Fig- I this tube, opposed multiplying cathodes 2tand 2| are connected through the tunable resonant circuit 16.Cathodes-25 and 26 are sensitized. as were cathodes 2 andliorsecondary'emission, and is at central spiral 21..

Output cathodes 2i and 2e are also positioned in opposed relation, theand 2! being positioned to form a cylinder, each being electricallyseparated, and output cathodes 28 and" are also connected in this case.the anode by tunable resonant circuit 20'. Output cathodesdo not emitsecondaries and may be of carbonized nickel, as explained above foroutput cathode 9. The anode 21 is supplied with tial from the anodebattery I9.

I also prefer to provide, preferably by means of a focusing coil llenergized by focusing source 3| underthe control ofa resistor 32, afeeble magnetic field in the tube with the lines of force axial, so thatthere will be a progression of the electron oscillation paths in thedirection from multiplier cathodes to output cathodes. For example, whenradio frequency is applied between the multiplier cathodes '25 and 28,either from a driver or by causing the two vmultiplying cathodesstructure, the electrons oi the proper phase for multiplication tend tooscillate so that they are traveling along the center line connectingthe multiplying cathodes,

and the electrons oscillating in the phase .to give. up their energy tothe output circuit 20 tend to swingaround at right angles to themultiplier cathodes. The application of the magnetic field effectivelyprevents the output electrons from swinging around, so that they areabsorbing power. There is therefore, due to'this field, a continuousdrift of multiplying electrons over to the output cathodes 28 and 29,where they are collected'aitergiving up their energy to the outputcircuit. f

The main advantage of this type oi structure over ,the structureheretofore described is that four cathodes 25,16, 28"

structure comprising cathodes Iv and a positive potenall of the; currentbuilt up by.multiplication is eventually converted into oscillatingpower, resulting in ,a very high emciency.

Other circuits utilizing the means and method herein described will.readily suggestthemselves to those skilled in the art, the circuitsshoWnbeing in the nature of examples only.

.Iclaim:

1. An electron multiplier comprising a pair of opposed surfaces capableof emitting secondary electrons at a ratio greater than unity whenimpacted, means for causing an oscillate between said surfaces-to createrepeated multiplying impacts therewith, means for divertinto aspaceapart from that bounded by said .suriaces, and means ing a portionof said cloud .ior absorbing power from said diverted portion withlnsaidspace. g

2. An electron multiplier comprising a' pair of opposed surfaces capableof emitting secondary electrons at a ratio greater than unity whenimpacted, means forcausing an electron cloud to oscillate between saidsurfaces to create repeated multiplying impacts therewith, one of saidsur- -faces being apertured to allow'a portion of said thus electron"cloud to;

r portions from the space bounded by said surfaces,

cloud to pass therethrough at the time of each impact, and means forabsorbing power from the electronspassing through said apertures.

3. Anelectron multiplier comprising a pair of opposed surfaces capableof emitting secondary electrons at a ratio greater than unity whenimpacted, means for causing an electron cloud to oscillate between saidsurfaces to createrepeated multiplying impacts therewith, means fordividing said cloud at the plane of one of said sur- Y faces, means forabstracting one of the divided portions from the space bounded by saidsurfaces, and means for absorbing power from the obtained.

abstracted portion.

4. An electron multiplier comprising a pair of opposed surfaces capableof emitting secondary electrons at-a ratio greater than unity whenimpacted, means for causing an electron cloud to oscillate between saidsurfaces to create repeated multiplying impacts therewith, means fordividing said cloud at the plane of one of said surfaces means forabstractingone of the divided portions from the space bounded by saidsurfaces, means for absorbing power from the abstracted portion, and awork circuit for utilizing the power 5. An electron multipliercomprising a pair of opposed surfaces capable of emitting secondaryelectrons at a ratio greater than unity when impacted, means for causingan electron cloud to oscillate between said surfaces to create repeatedmultiplying impacts therewith, means for dividing said cloud at theplane of one of said surfaces, means for abstracting one of the dividedmeans-for absorbing power from the abstracted portion, a work circuitfor utilizingthe power obtained, and means for feeding energy from saidwork circuit into said oscillating cloud.

6-. An electron multiplier comprising a pair of opposed surfaces capableof emitting secondary electrons at a ratio greater than unity whenimpacted, means for causing an electron cloud to oscillate between saidsurfaces to create repeated multiplying impacts therewith, means fordividing said cloud at the plane of one of said surfaces, means forabstracting one of the divided portions I from the space bounded by saidsurfaces, means and means for utilizing a portion of the energy' forabsorbing power from the abstracted portion,

a work circuit for utilizing the power obtained.

, in said work circuit to cause continued oscillation 'of said cloud.

7. 'An electron multiplier comprising a pair of opposed surfaces capableofemitting secondary electrons at a ratio greater than unity whenimpacted, means for causing an electron cloud to oscillate between saidsurfaces to create repeated multiplying impacts therewith, means fordividing said cloud at the plane of one of said surfaces,

- means for abstracting one of the divided portions for absorbing powerfrom the abstracted portion,

from the space bounded by said surfaces, means a work circuit forutilizing the power obtained,

and means for feeding back a portion of the energy in said work circuitinto said oscillatingcloud in the proper phase to continue theoscillation thereof.

-8. In an electron multiplier wherein electrons are directed against acathode surface to produce secondary emission therefrom, the methodofpower-production comprising oscillating elec-.

,set of paths, and

from the cloud through apertures in said surface a definite proportionof the electrons therein, and

absorbing the energy from the abstracted electrons. I

, 9. In an electron multiplier structure wherein an electron cloud isoscillated against and away from a surface to produce secondary emissiontherefrom upon impact therewith, the method of abstracting power fromsaid cloud which comprises feeding energy to said cloud and abstractingenergy from said cloud within different spatial boundaries.

10. In an electron multiplier structure wherein an electron cloud-isoscillated against and away from a surface to produce secondary emis-'sion therefrom upon impact therewith, the meth 0d of, abstracting powerfrom said cloud which comprises dividing said cloud at each impactfeeding energy to one portion of said cloud to continue multiplicationand abstracting useful energy from'the other portion.

11. In an electron multiplier structure wherein an electron cloud isoscillated against and away from a surface to produce secondary emissiontherefrom upon impact therewith, the method of abstracting power fromsaid cloud which comprises absorbing energy from said cloud, using' saidenergy to sustain oscillation of said cloud until an equilibrium currentis reached, abstractingelectrons from said cloud, absorbing energy fromsaid abstracted electrons, and adding said energy to that previouslyabsorbed from said cloud to create regenerative oscillation thereof.

12. In an electron multiplier structure wherein an electron cloud isoscillated againstand away from a surface to produce secondary'emissiontherefrom upon impact therewith,- the method of abstracting power fromsaid cloud I which comprises feeding energy to electrons traveling alongone set of paths, changing the paths,- and abstracting power fromsaidelectrons while in said changed paths.

' 13. In an electron multiplier structure wherein an electron cloud isoscillated against and away from a surface to produce secondary emis-'sion therefrom upon impact therewith, the method of abstracting powerfrom said. cloud which comprises feeding energy to electrons travelingalong a diametrical path, shifting the' electrons to. a differentdiametrical path, and absorbing power different path.

' 14. In an electron multiplier structure wherein an electron cloud isoscillated against and away from a surface to produce secondary-emissiontherefrom upon impact therewith, the method of abstracting power fromsaid cloud 'whioh comprises feeding energy to electrons traveling alongone set of paths, continuously diverting a portion of said cloud into adifferent absorbing. energy from said electrons while in saiddifl'erentpaths.

15. In an .electron multiplier structure where- .in an electron cloud-isoscillated against and away from a surface to produce' secondaryemission therefrom upon impact therewith, the method. of abstractingpower from said cloud which comprises feeding energy to said cloud tofrom said eledtrons while in said 'maintain oscillation of the cloudacross a space in a predetermined path, shifting the oscillation to adifferent predetermined path, and absorbing power from the electrons inthe latter path.

16.- In combination, a pair of opposed electrodes capable of emittingsecondary electrons at 'a ratio greater than unity, a second pair of op-I 9,091,439 5 posed electrodes inca able of emitting secondary cousinsle tr n oscillati n between said first electrons. adjacent saidfirstpair, means for pair of electrodes to cause secondary emission feedingenergy to electrons in the space between therefrom, means for rotatingthe oscillation said first pair oi electrodes to produce electron patharound the axis of said cylinder, and means 5 multiplication by cyclicalimpact therewith, and associated with said second pair of electrodes 5means associated with said second pair of elecfor absorbing power fromelectrons in said rotrodes for absorbing power from said electrons.tated path. 1

17. Incombinatiomapair oi opposedelectrodes a 19. In combination, a pairof opposed eleccapable of emitting secondary electrons at-a trodescapable of emitting'secondary electrons. lo ratio greater than unity, asecond pair of opat a ratio greater than unity, a second pair of 10posed electrodes incapable of emitting secondary opposed electrodesincapable of emitting secondelectrons, said pairs being alternatelydisposed ary electrons, said pairs being alternately disto describe asymmetrical space, means for ieedposed to describe a cylindrical space,means for ing energy to electrons in the space between said causingelectron oscillation between said first pair 15 first pair 01'electrodes to produce electron muloi electrodes to cause secondaryemission there- 15 tiplication by cyclical impact therewith, and from,means for rotating the oscillation path means associated with secondpairof electrodes around the axis oi said cylinder, means associforabsorbing power from said electrons. ated with said second pair oielectrodes for ab- 18. In combination, a pair of opposed elecsorbingpower from electrons in said rotated 20 trodes capable of emittingsecondary electrons path. and means for collecting electrons contact- 20.at a ratio greater than unity, a second pair of ing said'second pair ofelectrodes due to said opposed electrodes incapable of emittingsecondrotation. ary electrons, said pairs being alternately dis- PHILOT. FARNSWORTH. posed to describe a cylindrical space, means for vGERTIFICATEOF comancrror. Patent No. 2,o91,l 9, August 1951 v 91111.01'. FARNSWORTHI.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows: Page 2,second column, line 71;, forthe word "members" read numbers; and thatthe said Letters Patent shonldbe read with this correction therein thatthe samemay conform to the recorder the case in the Patent Office..

Signed and sealed this 1 th day of October, A. D. ;l958.

Henry Van Arsdale- (Seal) I Acting Commissioner of Patents.

DISCLRIMER f 2,091,439.-Philo T. Fm San Francisco Calif Mon'rrANn'AMPmrmn; Ifate'nt dated A st 3l l937. DisJ3:fez- 512a 31 s;31 2:1

R 5b, 1942, by the assig nee, Famswo Television & Radio Corporation.

specifigteioienters this disclaimer to claims 1, 3, 4, 8, 9, 10, 12, 14,15, and 16 in said' [Qfi Gazette January 27, 1942.]

I 9,091,439 5 posed electrodes inca able of emitting secondary cousinsle tr n oscillati n between said first electrons. adjacent saidfirstpair, means for pair of electrodes to cause secondary emission feedingenergy to electrons in the space between therefrom, means for rotatingthe oscillation said first pair oi electrodes to produce electron patharound the axis of said cylinder, and means 5 multiplication by cyclicalimpact therewith, and associated with said second pair of electrodes 5means associated with said second pair of elecfor absorbing power fromelectrons in said rotrodes for absorbing power from said electrons.tated path. 1

17. Incombinatiomapair oi opposedelectrodes a 19. In combination, a pairof opposed eleccapable of emitting secondary electrons at-a trodescapable of emitting'secondary electrons. lo ratio greater than unity, asecond pair of opat a ratio greater than unity, a second pair of 10posed electrodes incapable of emitting secondary opposed electrodesincapable of emitting secondelectrons, said pairs being alternatelydisposed ary electrons, said pairs being alternately disto describe asymmetrical space, means for ieedposed to describe a cylindrical space,means for ing energy to electrons in the space between said causingelectron oscillation between said first pair 15 first pair 01'electrodes to produce electron muloi electrodes to cause secondaryemission there- 15 tiplication by cyclical impact therewith, and from,means for rotating the oscillation path means associated with secondpairof electrodes around the axis oi said cylinder, means associforabsorbing power from said electrons. ated with said second pair oielectrodes for ab- 18. In combination, a pair of opposed elecsorbingpower from electrons in said rotated 20 trodes capable of emittingsecondary electrons path. and means for collecting electrons contact- 20.at a ratio greater than unity, a second pair of ing said'second pair ofelectrodes due to said opposed electrodes incapable of emittingsecondrotation. ary electrons, said pairs being alternately dis- PHILOT. FARNSWORTH. posed to describe a cylindrical space, means for vGERTIFICATEOF comancrror. Patent No. 2,o91,l 9, August 1951 v 91111.01'. FARNSWORTHI.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows: Page 2,second column, line 71;, forthe word "members" read numbers; and thatthe said Letters Patent shonldbe read with this correction therein thatthe samemay conform to the recorder the case in the Patent Office..

Signed and sealed this 1 th day of October, A. D. ;l958.

Henry Van Arsdale- (Seal) I Acting Commissioner of Patents.

DISCLRIMER f 2,091,439.-Philo T. Fm San Francisco Calif Mon'rrANn'AMPmrmn; Ifate'nt dated A st 3l l937. DisJ3:fez- 512a 31 s;31 2:1

R 5b, 1942, by the assig nee, Famswo Television & Radio Corporation.

specifigteioienters this disclaimer to claims 1, 3, 4, 8, 9, 10, 12, 14,15, and 16 in said' [Qfi Gazette January 27, 1942.]

